In Japanese Kokai Publication Hei-09-272714, among others, there is disclosed a curable composition which comprises an alkenyl group-containing vinyl polymer and a hydrosilyl group-containing compound and is capable of curing via the hydrosilylation reaction.
However, the viscosity of the above composition, the main component of which is a polymer, is not always low and, therefore it is necessary to improve the composition with respect to its workability, processability and so forth. The method generally employed for reducing the viscosity comprises diluting the composition with a plasticizer or the like having a lower viscosity as compared with the main component. However, a nonreactive plasticizer does not participate in the curing reaction, hence is not bonded to the network of the crosslinked product, so that marked decreases in mechanical properties, heat resistance and other properties as resulting from the addition of a plasticizer cannot be avoided. As for the heat resistance, in particular, the plasticizer evaporation at high temperatures is a problem, and method of improvement in that respect has been searched for.
On the other hand, the polymer mentioned above has a property such that the viscosity decreases as the temperature increases. If compositions containing the above-mentioned polymer are handled at temperatures higher than ordinary temperature making good use of such property, the workability may presumably be secured and, in addition, any decrease in reliability with respect to physical properties will probably not be caused.
However, the above composition is very poor in storage stability at room temperature and higher temperatures and it tends to gelate readily at elevated temperatures.
Furthermore, the curing products obtained from the above curable composition are required to have higher strength properties in certain fields of utilization.